JP2007095469A - Chip fuse device and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the resistance of a fuse element and to facilitate the control of the resistance value of the fuse element, in a chip type fuse device composed by forming a fuse element by using, for instance, a low-cost printing method. <P>SOLUTION: The chip fuse device is provided with the fuse element having a porous structure. When the fuse element is formed by printing fuse element paste containing meta particles and by sintering the metal particles in an oxidizing atmosphere, fuse element paste containing volatile particles vaporizing by the sintering is used. It is preferable that graphite particles are used as the volatile particles. It is preferable that at least one kind selected from Ag particles and Au particles is used for the metal particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a chip-type fuse element having a novel fusible body and a method for manufacturing the same.

  As a chip-type fuse element, one having a structure in which a narrow fusible body made of a metal film or the like is formed on an insulating substrate and terminal electrodes are connected to both ends of the fusible body is known. As a method for forming such a soluble material, there is a method using a thin film method such as vapor deposition or sputtering (see, for example, Patent Document 1, Patent Document 2, etc.). In this method, after forming a thin soluble body by a thin film method, thinning can be achieved by a lithography technique, and there is an advantage that the resistance of the soluble body can be easily increased. However, a thin film method such as vapor deposition or sputtering requires a vacuum technique and requires a large-scale manufacturing facility, which causes a problem that the cost of the chip-type fuse element is significantly increased.

In recent years, therefore, printing methods have attracted much attention. For example, Patent Document 3 describes that a soluble material is formed using a thick film technique based on screen printing of an Ag-based paste. Since the printing method does not require a large-scale production facility required for vapor deposition or sputtering, it is expected as a method that can greatly reduce the manufacturing cost of the chip-type fuse element.
JP-A-6-176680 JP 2003-173728 A JP 2002-140975 A

  However, a chip-type fuse element in which a fusible body is formed by a printing method has limitations in thinning and thinning the fusible body, so that it can be used in comparison with the fusible body formed by the thin film method (evaporation, sputtering). The cross-sectional area of the solution tends to increase. Therefore, the resistance value of the fusible body formed by the printing method is low, and as a result, there is a problem that Joule heat necessary for fusing the fusible body cannot be ensured and good fusing characteristics cannot be obtained.

  In addition, a manufacturer of chip-type fuse elements needs to prepare chip-type fuse elements having different current values (rated currents) that are fused in accordance with the user's application. Since the rated current is generally determined by the resistance value of the fusible body, a method of easily controlling the resistance value of the fusible body is important when manufacturing a chip-type fuse element having various resistance values.

  Therefore, the present invention has been proposed in view of such a conventional situation. For example, in a chip-type fuse element in which a fusible body is formed using a low-cost printing method, the fusible body has a high resistance. An object of the present invention is to provide a chip-type fuse element that can easily control the resistance value of a fusible body and a method for manufacturing the same.

  In order to achieve the above-described object, a chip-type fuse element according to the present invention includes a fusible body having a porous structure.

  In the fusible body of the chip-type fuse element as described above, a large number of voids are present in the fusible body to reduce the proportion of the fusible material per unit volume. Therefore, the effective cross-sectional area of the fusible body is reduced as compared with the conventional dense fusible body, and even if the actual cross-sectional area of the fusible body is thick, the fusible body showing a high resistance value is obtained. Realized. In addition, in the chip type fuse element as described above, the resistance value of the fusible element can be arbitrarily controlled by changing the ratio of the metal to the air gap, so that chip type fuse elements of various standards (rated current) are realized. Is done.

  In addition, a method for manufacturing a chip-type fuse element according to the present invention includes a chip-type fuse element that forms a soluble body by printing a soluble paste containing metal particles and sintering the metal particles in an oxidizing atmosphere. It is a manufacturing method, Comprising: The said soluble body paste contains the volatile particle | grains volatilized by the said sintering. Furthermore, the method for manufacturing a chip-type fuse element according to the present invention is possible by printing a soluble paste containing metal particles, heat-treating in an oxidizing atmosphere, and then sintering the metal particles in a reducing atmosphere. A method of manufacturing a chip-type fuse element for forming a solution, wherein the soluble paste includes volatile particles that volatilize by the heat treatment.

  By including the volatile particles for forming the porous structure in the soluble paste, formation of a soluble body having a porous structure and showing a high resistance value is realized. Further, by changing the blending ratio of various particles in the soluble paste, the abundance ratio between the metal and the void in the soluble body can be controlled, and as a result, the resistance value of the soluble body can be controlled. Therefore, even when a printing method with large material restrictions is used, a soluble material having a desired resistance value is easily formed. Furthermore, since the printing method is used, cost reduction that is an advantage of the printing method is realized.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the chip-type fuse element which implement | achieved high resistance of a soluble body and was excellent in the fusing characteristic, utilizing the printing method which is difficult to make a thin line and a thin film. In addition, according to the present invention, the resistance value of the fusible body can be controlled by controlling the ratio of the metal to the gap in the fusible body, so that the design flexibility of the chip-type fuse element is improved and the chip having various rated currents A mold fuse element can be provided.

  Hereinafter, a chip-type fuse element to which the present invention is applied and a manufacturing method thereof will be described in detail with reference to the drawings.

  A chip-type fuse element to which the present invention is applied basically includes a chip-like substrate 1 and a fusible body 2 formed on the substrate 1, as shown in FIGS. 1 (a) and 1 (b). is there. Here, the fusible body 2 may be formed into a thick film using a printing method or a thin film using a sputtering method or the like, but when a thin film method such as a sputtering method is used. The printing method is a suitable technique in that the manufacturing cost can be greatly reduced as compared with that a low-cost chip-type fuse element can be provided. Therefore, the following description will be made mainly assuming a chip-type fuse element having a fusible body 2 formed by a printing method.

The board | substrate 1 becomes a support body of the soluble body 2, for example, is formed in square shape. The material constituting the substrate 1 is not limited, and any material used for this type of chip-type fuse element can be used. As a material constituting the substrate 1, for example, an insulating material exhibiting low thermal conductivity can be used, and more specifically, an insulating material such as Al ₂ O ₃ or glass ceramic can be used.

  The fusible body 2 is intended to protect an electric circuit or the like in which a chip-type fuse element is incorporated by fusing when an excessive current that exceeds twice the rated current flows, for example. The chip-type fuse element of the present invention is characterized in that the fusible body 2 has a porous structure. Although the details will be described later, the porous structure of the soluble body 2 is formed by, for example, including the volatile particles having a predetermined size in the soluble body paste and volatilizing the volatile particles during firing of the soluble body paste. Is.

  The “porous structure” in the present invention means that the ratio of the soluble metal is 90 when the structure photograph of the cross section of the soluble body is analyzed by image analysis software and the area ratio between the void portion and the soluble metal portion is calculated. % Refers to the case of less than or equal to%. For example, when a soluble material is formed by a printing method, the metal particles are densified by decreasing the gaps between the metal particles during the sintering process, but the gaps are not completely eliminated. For this reason, countless extremely fine spaces remain in the conventional soluble body. However, when considering increasing the resistance of the fusible body, such an inevitable fine space is meaningless. In the present invention, it is important to actively form a relatively large amount of voids such that the ratio of the soluble metal is 90% or less by using, for example, volatile particles as described later.

  Examples of the metal constituting the soluble body 2 include Ag, Au, Pt, and Cu. Especially, since baking in air | atmosphere is attained without requiring special control, 1 type chosen from Ag, Au, and Pt is preferable, and Ag and Au are especially preferable and Ag is especially preferable.

  The planar shape of the fusible body 2 is, for example, a shape having a narrow narrow portion between the electrodes 3 as shown in FIG. 1, but is not limited thereto, and can be various shapes.

  Terminal electrodes 3 serving as external electrodes are connected to both ends of the fusible body 2. The configuration of the terminal electrode 3 is not particularly limited. For example, the terminal electrode 3 is composed of a thick film containing a good conductive material such as Ag, Pt, or Pd, a plating film of the good conductive material, a resin containing the good conductive material, or the like. .

The chip-type fuse element generally includes a protective layer 4 that covers the fusible body 2. The protective layer 4 reliably insulates the melted fusible body 2 when the fusible melt 2 is blown by an overcurrent exceeding a predetermined current value flowing through the fusible melt 2 and scatters the material constituting the fusible melt 2. It is what prevents. As the protective layer 4, for example, glass such as ZnO-based glass, CaO-based glass, Bi ₂ O ₃ -based glass, SrO-based glass, silicone resin, or the like can be used.

  Furthermore, as shown in FIG. 2, a heat storage layer 5 may be disposed between the substrate 1 and the soluble body 2 as necessary. Although it does not specifically limit as a material which comprises the thermal storage layer 5, It is preferable to use the material which shows low heat conductivity, For example, glass etc. can be mentioned. The heat storage layer may have a porous structure.

  In the chip-type fuse element as described above, since the fusible body 2 has a porous structure, the effective cross-sectional area is assumed to be small. Therefore, even if the actual cross-sectional area of the fusible body 2 is large, the resistance of the fusible body 2 can be increased. As a result, shortening of the fusing time and low current fusing are achieved, and the fusing characteristics can be improved.

  Moreover, the resistance value of a soluble body can be controlled to a desired value by changing the ratio of the metal and the space | gap in the soluble body 2. FIG. For this reason, a desired resistance value can be obtained in the chip-type fuse element.

  In the manufacturing method of the chip-type fuse element as described above, the fusible body is composed of a metal that is relatively difficult to oxidize such as Ag, Au, and Pt, and the case that the fusible body is composed of a metal that is relatively easily oxidized such as Cu And can be roughly divided. Below, the manufacturing method of the chip-type fuse element which uses at least 1 sort (s) chosen from Ag, Au, Pt etc. as a soluble metal is demonstrated first.

  First, a soluble paste is printed on the substrate 1 in a predetermined shape by, for example, screen printing. The soluble paste used here contains at least metal particles and volatile adult particles, which are prepared by mixing with an organic vehicle.

  As the metal particles contained in the soluble paste, for example, metal particles containing at least one selected from Ag, Au, Pt and the like are preferable. Ag, Au, and Pt are suitable materials for forming the fusible body 2 by the printing method because they can be fired in the air without requiring special control. Of these, Ag and Au are preferable, and Ag is particularly preferable.

  Volatile particles refer to particles that can form a porous structure as defined above by volatilization. As the volatile particles, carbon particles that are materials that volatilize around the temperature at which the metal particles are sintered can be used. In particular, carbon particles that volatilize around the sintering temperature for sintering the metal particles are preferable. Specifically, it is preferable to use carbon particles having a volatilization temperature Tc that satisfies the relationship of the following formula (1) when the sintering temperature is T1 ° C. If the volatilization temperature Tc of the volatile particles is lower than the sintering temperature T1-200 ° C, the porous structure may not be formed. Conversely, if the volatilization temperature Tc of the volatile particles is equal to or higher than the sintering temperature T1, the volatile particles are volatile. Particle volatilization may not proceed. Examples of the carbon particles satisfying the relationship of the formula (1) include graphite particles.

  T1-200 <Tc <T1 Formula (1)

  The organic vehicle has a role of making various powders into a paste, and any of those used for this type of paste can be used. An organic vehicle is prepared by dissolving a binder in an organic solvent. It does not specifically limit as a binder, For example, what is necessary is just to select suitably from various binders, such as an ethyl cellulose and polyvinyl butyral. The organic solvent is not limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene. Furthermore, in order to adjust the physical properties of the soluble paste, various additives such as a dispersant may be added.

  The organic vehicle is a material that volatilizes by heat treatment, but cannot form a porous structure as defined above. Therefore, the organic vehicle is not included in the volatile particles referred to in the present invention.

  After the soluble paste is printed, it is fired. Thereby, the binder in the soluble paste is removed, and the metal particles in the soluble paste are sintered. In addition, voids are formed by volatilizing volatile particles in the soluble paste during the firing. Therefore, a soluble body 2 having a porous structure in which a large number of voids exist in the metal is formed.

  Since it is necessary to volatilize the organic binder and volatile particles in the soluble paste, the firing atmosphere can be an oxidizing atmosphere, specifically an air atmosphere.

  Next, the terminal electrode 3 is formed on the substrate 1. For example, in order to form the terminal electrode 3 with a thick film, a conductive paste containing, for example, Ag, Pt, Pd or the like may be dipped and fired. The terminal electrode 3 is not limited to being formed after the fusible body 2 is formed, but may be formed in advance before the fusible body 2 is formed. Further, the terminal electrode 3 and the fusible body 2 may be fired simultaneously.

  Next, the protective film 4 is formed so as to cover the formed soluble body 2. As described above, the chip-type fuse element having the structure shown in FIG. 1 is manufactured.

  For example, when a soluble material is formed by a printing method using a conventional soluble material paste containing metal particles such as Ag, there is a limit to so-called high definition such as reducing the line width and film thickness of the soluble material. It is difficult to increase the resistance of soluble materials. On the other hand, in the present invention, the soluble body 2 having a porous structure is formed by, for example, replacing a part of metal particles with volatile particles and firing. By making the fusible body 2 have a porous structure, the volume of the metal part that actually functions as the fusible body 2 is reduced, and the effective cross-sectional area of the fusible body 2 is reduced. For this reason, even if it is a case where the printing method in which high definition is difficult is used, the soluble body 2 which has high resistance value can be formed. Further, the cost reduction that is an advantage of the printing method can be realized.

  Moreover, in the manufacturing method of the chip-type fuse element as described above, the resistance value of the obtained fusible body 2 is set to an arbitrary value by changing the mixing ratio of the metal particles and the volatile particles contained in the fusible paste. Can be designed easily. Since the resistance value of the fusible body 2 can be easily designed, chip-type fuse elements having various resistance values can be easily manufactured even when the printing method is used.

  Conventionally, the resistance value of the soluble body was controlled by changing the dimensions of the soluble body, but according to the present invention, the resistance value can also be controlled by changing the amount of volatile particles added to the soluble body paste. Therefore, the design flexibility of the chip-type fuse element can be increased.

  Hereinafter, a method for manufacturing a chip-type fuse element using Cu as a fusible metal will be described. Detailed description of the same parts as those in the above manufacturing method will be omitted.

  First, a soluble paste is prepared. The soluble paste used here contains at least Cu particles as metal particles and volatile particles, and is prepared by mixing with an organic vehicle. Here, the volatile particles can be the same as those used when Ag, Au, Pt or the like is used as the metal. The same applies to organic vehicles.

  After the soluble paste is printed in a predetermined shape by, for example, screen printing, the soluble paste is fired. When firing, it is necessary to remove the binder in the soluble paste, sinter the metal, and volatilize the volatile particles in the soluble paste, as in the case of containing Ag or the like as the soluble body. However, if firing is performed in an oxidizing atmosphere as in the case of Ag or the like, Cu may be oxidized. For this reason, when Cu is used as the fusible metal, as described below, the printed fusible paste is heat-treated in an oxidizing atmosphere, and then Cu is sintered in a reducing atmosphere.

  That is, first, the soluble paste after printing is heat-treated in an oxidizing atmosphere. The heat treatment here serves as both a binder removal process for removing the binder in the soluble paste and a process for volatilizing the volatile particles. Therefore, the heat treatment temperature is set to be equal to or higher than the volatilization temperature Tc of the volatile particles. Further, since it is necessary to remove the binder in the soluble paste and volatile particles such as carbon particles, the heat treatment atmosphere may be an oxidizing atmosphere, specifically, an air atmosphere. The heat treatment removes the binder in the soluble paste and volatilizes the volatile particles to form voids in the soluble Cu oxide.

Next, Cu is sintered. The void formed in the previous heat treatment remains after sintering, whereby a soluble body made of Cu having a porous structure is formed. The sintering atmosphere is, for example, a reducing atmosphere containing H ₂ in order to reduce Cu oxidized by the heat treatment.

  Thereafter, the terminal electrode 3 and the protective film 4 are formed. Through the above steps, a chip-type fuse element including a soluble body 2 having a porous structure using Cu, which is a metal that is easily oxidized, as a soluble body metal is manufactured.

  In the above description, the case where a soluble body having a porous structure is formed by using a printing method and volatilizing volatile particles has been described as an example. However, the chip-type fuse element of the present invention is limited to these methods. Is not to be done.

  For example, an alloy film is formed on a substrate by any method such as a printing method, a thin film forming method such as sputtering, vapor deposition, plating, etc., and then a solubilized body having a porous structure is formed by dipping in an acidic solution. Can do. Since the solubility with respect to an acid changes with metals, the porous structure can be obtained by dissolving a part of the metal constituting the alloy film by selecting an appropriate acidic solution.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. Needless to say, the present invention is not limited to the following examples.

Example 1
First, a soluble paste was prepared. Metal Ag particles (average particle size 0.1 μm), graphite particles (average particle size 1 μm), and organic vehicle were weighed so as to have each composition, and kneaded with a three-roll mill to obtain a soluble paste. The mixing ratio (mass%) of the metal Ag particles and the graphite particles was in accordance with the description in Table 1. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent. The mixing ratio of the metal Ag particles and graphite particles to the organic vehicle was set so that the obtained resistor paste had a viscosity suitable for screen printing.

  Next, in the printing process, the soluble paste was screen-printed on the substrate in the shape shown in FIG. 1 and dried. When printing the fusible paste, it was applied so that the film thickness of the fusible body after firing was 20 μm, the width of the narrow portion was 100 μm, and the length was 2.5 mm. Alumina was used as the substrate. Then, this board | substrate was put into the belt furnace, the binder in a paste was removed in air | atmosphere, and it baked. The heat treatment temperature during firing was 900 ° C., and the holding time at that temperature was 5 minutes. By this firing, a soluble material having a porous structure was obtained.

  Next, an Ag thermosetting resin was dipped at both ends of the fusible body, and then thermosetting was performed to form external electrodes, thereby obtaining a chip-type fuse element.

  The resistance value and the fusing time were measured for the obtained chip-type fuse element of each sample. The fusing time was defined as the time from when the current of 4 A started to flow through the soluble material until the soluble material was cut. The results are shown in Table 1.

  As is clear from the results in Table 1, it is possible to increase the resistance of the fusible body and shorten the fusing time by including graphite particles in the fusible paste and making the fusible body have a porous structure. Recognize. In addition, particularly good results have been obtained by setting the content ratio of Ag particles to graphite particles in the range of 88:12 to 96: 4 (mass%).

(Example 2)
In the present Example, it examined using Cu as a soluble metal.
First, a soluble paste was prepared. Metal Cu particles (average particle size 1 μm), graphite particles (average particle size 1 μm), and organic vehicle were weighed so as to have each composition and kneaded by a three-roll mill to obtain a soluble paste. The mixing ratio (mass%) of the metal Cu particles and the graphite particles was in accordance with the description in Table 2. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent. The compounding ratio of the metal Cu particles and graphite particles to the organic vehicle was set so that the obtained resistor paste had a viscosity suitable for screen printing.

  Next, in the printing process, the soluble paste was screen-printed on the substrate in the shape shown in FIG. 1 and dried. When printing the fusible paste, it was applied so that the film thickness of the fusible body after firing was 20 μm, the width of the narrow portion was 100 μm, and the length was 2.5 mm. Alumina was used as the substrate. Thereafter, this substrate was put in a belt furnace and heat-treated at 800 ° C. in an air atmosphere. By this heat treatment, the graphite particles were volatilized and voids were formed in the Cu oxide.

Next, Cu oxidized by the heat treatment was reduced by heat treatment in a reducing atmosphere, and Cu was sintered. Specifically, oxidized Cu was reduced by holding at 400 ° C. for 30 minutes in an N ₂ -4% H ₂ atmosphere. Subsequently, _{N 2} atmosphere, and held for 5 minutes at 900 ° C., was sintered Cu. Thereby, a Cu soluble body having a porous structure was obtained.

  Next, an Ag thermosetting resin was dipped at both ends of the fusible body, and then thermosetting was performed to form external electrodes, thereby obtaining a chip-type fuse element.

  The resistance value and the fusing time were measured for the obtained chip-type fuse element of each sample. The fusing time was defined as the time from when the current of 4 A started to flow through the soluble material until the soluble material was cut. The results are shown in Table 2.

  As is clear from the results in Table 2, when Cu is used as the soluble metal, similarly to the result of Experiment 1, the soluble paste contains graphite particles, and the soluble body has a porous structure. It can be seen that the resistance of the fusible body is increased and the fusing time is shortened.

It is a figure which shows an example of the chip-type fuse element to which this invention is applied. (A) is a schematic plan view, (b) is a schematic sectional drawing. It is a schematic sectional drawing which shows the other example of the chip-type fuse element to which this invention is applied.

Explanation of symbols

  1 substrate, 2 fusible body, 3 electrodes, 4 protective layer, 5 heat storage layer

Claims (13)

  A chip-type fuse element comprising a fusible body having a porous structure.   2. The chip-type fuse element according to claim 1, wherein the fusible body includes at least one selected from Ag and Au.   The chip-type fuse element according to claim 1 or 2, wherein the fusible body is formed by a printing method. A method for manufacturing a chip-type fuse element, in which a fusible paste containing metal particles is printed and a fusible body is formed by sintering the metal particles in an oxidizing atmosphere,
The method for manufacturing a chip-type fuse element, wherein the fusible paste includes volatile particles that volatilize by the sintering.   5. The method of manufacturing a chip-type fuse element according to claim 4, wherein carbon particles are used as the volatile particles. 6. The chip-type fuse element according to claim 5, wherein carbon particles satisfying the relationship of the following formula (1) are used when the volatilization temperature of the carbon particles is Tc.degree. C. and the sintering temperature is T1.degree. Manufacturing method.
T1-200 <Tc <T1 Formula (1)   7. The method for manufacturing a chip-type fuse element according to claim 6, wherein graphite particles are used as the carbon particles.   The method for manufacturing a chip-type fuse element according to any one of claims 4 to 7, wherein at least one selected from Ag particles and Au particles is used as the metal particles. A method of manufacturing a chip-type fuse element, wherein a fusible body paste containing metal particles is printed, heat-treated in an oxidizing atmosphere, and then the metal particles are sintered in a reducing atmosphere to form a fusible body.
The method for manufacturing a chip-type fuse element, wherein the fusible paste includes volatile particles that volatilize by the heat treatment.   The method for manufacturing a chip-type fuse element according to claim 9, wherein carbon particles are used as the volatile particles. 11. The chip-type fuse element according to claim 10, wherein carbon particles satisfying the relationship of the following formula (1) are used when the volatilization temperature of the carbon particles is Tc ° C. and the temperature of the heat treatment is T1 ° C. 11. Production method.
T1-200 <Tc <T1 Formula (1)   12. The method for manufacturing a chip-type fuse element according to claim 11, wherein graphite particles are used as the carbon particles.   The method for manufacturing a chip-type fuse element according to claim 9, wherein Cu particles are used as the metal particles.

Images